The proposed work will be on the structure and function of the Mg2+-ATPase located in the transverse tubular membrane system of mammalian skeletal muscle. The physiological function of this protein is unknown, but it is clearly structurally unrelated to the well characterized cation transporting ATPases also present in skeletal muscle. The long term goals are to better understand the role of the transverse tubules in excitation/contraction coupling and to understand the general principles underlying the structural basis for function among the class of proteins known as ATPases. The immediate goals are the elucidation of the structure and function of the transverse tubule Mg2+-ATPase. The work on the Mg2+-ATPase will, involve the identification, purification, and affinity labelling of the protein(s) involved, as well as the elucidation of possible physiological functions. Polyclonal antibodies will be raised to immunolocalize the Mg2+-ATPase. N-terminal as well as internal protein sequence will be obtained on all putative sub-units, and the entire amino acid sequence will be deduced from the cDNA sequence. Models of the structure of the Mg2+-ATPase will be proposed and the structure compared to other possibly related proteins. This work will generate important information about a component of the transverse tubule membrane system, the Mg2+-ATPase, and its relationship to the process of excitation/contraction coupling, a very important yet poorly understood physiological process.